This invention relates to a mechanism and a method for coating a powdery mold releasing agent on a cavity surface, in a casting work and especially in a die casting work.
A mold releasing agent for use in the die casting work is roughly classified into a water-soluble mold releasing agent and an oily mold releasing agent. Since the oily mold releasing agent includes such problems as causing a danger of inflammability and worsening of a work environment due to fuming smoke etc., the water-soluble mold releasing agent has been used more frequently than the oily mold releasing agent. However, the water-soluble mold releasing agent includes such a problem as requiring a cost for operation and a cost for equipment in order to treat waste water after use. While, a quality level of cast product is becoming high, at present. For this reason, a powdery mold releasing agent which can eliminate the cost for treating the waste water after use and is more excellent in mold releasing ability, has become used more frequently.
The powdery mold releasing agent is generally composed of an inorganic powder such as graphite, talc etc. and an organic powder such as wax, resin, metal soap etc. for enhancing adhesiveness of the inorganic powder onto the cavity surface. Since the powdery mold releasing agent is used under a powdery state, the powdery mold releasing agent disperses into atmosphere to deteriorate the work environment when the powdery mold releasing agent is spray-coated onto the cavity surface while opening the metal mold as in case of the oily mold releasing agent and the water-soluble mold releasing agent. Therefore, the powdery mold releasing agent is used while closing the metal mold.
The powdery mold releasing agent has so far been supplied from a sleeve of molten metal injection portion through a runner into a cavity. However, this supply method has included such a problem as being unable to obtain a cast product of high quality due to following troubles.
(1) Since the powdery mold releasing agent adheres to sleeve inside surface and runner, seizure occurs on the cast product due to insufficiency of a supply of powdery mold releasing agent to the cavity.
(2) The powdery mold releasing agent deposits around the runner so as to impair smooth flow of molten metal, so that the molten metal does not spread completely into the cavity to cause inaccuracy of the shape and size of cast product.
(3) The powdery mold releasing agent adhering to the sleeve inside and runner flows together with the molten metal and is caught up in it, so that the powdery mold releasing agent becomes a cause of inside defect of the cast product.
An object of this invention is to provide a coating mechanism and a coating method of powdery mold releasing agent for dissolving the foregoing problems and obtaining a cast product of high quality even when the powdery mold releasing agent is used.
A first invention of this application comprises a mechanism for coating the powdery mold releasing agent onto a cavity surface in the casting work; characterized by that the mechanism has a powder supply means for supplying the powdery mold releasing agent to a basin and a pressure reduction means for reducing a pressure in the cavity, so that the powdery mold releasing agent is supplied to the basin while operating the pressure reduction means.
A second invention of this application comprises a method for coating the powdery mold releasing agent onto a cavity surface in the casting work; characterized by that the powdery mold releasing agent is supplied through the basin into the cavity while reducing a pressure in the cavity.